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PV-Battery Integrated Module

Víctor Vega Garita

Vermogenselektronica 20th of June 2017

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Motivation

• Current PV-battery systems are complex and

costly. Disadvantages

High

installation

cost

A lot of

space used

Low

integration

degree

Source: Saft Batteries

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Our idea • Integrate all components of a PV-battery system

in one device

• Advantages:

– Plug and play solution

– Reduction of installation cost

– Space saving solution

– Modular approach

– Portable solution

Pouch cells

Charge controller

(MPPT)

PV module

Microinverter

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Design considerations

• Thermal behavior

– Aging, volume vs. weight, and safety

• Battery technology

– C-rate and aging

• Optimum battery capacity

– Storage motivations and cost

• PV-battery electrical architecture

– Efficiency and cost

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Analysis of thermal behavior

• To determine operational conditions under

severe cases

• To evaluate Phase Change Materials as a heat

management solution

How to study the thermal behaviour?

• Thermal model using Finite Elements Method

(FEM)

• Select an appropriate study case

• Test a lab prototype for validation purposes

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FEM Model

• Heat conduction in solids

• Heat conduction in liquids

• Fluid dynamics

(1)

(2)

(3)

(4)

EVA

layersSi layerTedlar layer

ConverterCell 1

Aluminum frame

Glass layer

Air domain

PV

panel

Open boundary

or inlet

Open boundary

or outlet

Cell 2 Cell 3PCM PCM PCM

Air gap

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• Inputs

– Three days with highest ambient temperature,

highest solar irradiance, and lowest wind speed

in a year for NL.

a) b)

c) d)

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• System specification

Solar panel

Power 265 Wp

Open circuit voltage 38.6 V

Short circuit current 9.06 A

Efficiency 16.19 %

Power coefficient -0.41 %/°C

Battery (LiFePO4)

Capacity ≈ 1 kWh

Battery nominal voltage 3,2 V

Maximum temperature 55 °C

Specific energy 131 Wh/kg

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Results • Directly attached or not?

a) u = 1 m/s b) u = 8 m/s

c) u = 1 m/s d) u = 8 m/s

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• Directly attached or not?

• Optimal air gap

a)

c)

b)

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• PV temperature

• Battery pack temperature and PCM a)

b) c)

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• Validation

Charge Controller

(MPPT)

Load

Battery

PV panel

c) b) a)

d) e)

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Conclusion

• Air gap helps to reduce the temperature of the components.

• An air gap of 5-7 cm provides an appropriate packaging/cooling efficiency ratio.

• Batteries operate in safe a temperature range even under severe conditions.

• Phase change material is a useful heat management solution, it reduces by 5 °C the maximum battery

temperature.

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Questions?